As it faces production issues with its highly anticipated next-generation smartphone lineup, Apple might be forced to delay the 5.5-inch model of its so-called "iPhone 6" until 2015.
This is according to Ming-Chi Kuo, a well-regarded Apple analyst at KGI Securities.
In a new research note to investors, Kuo says that issues with the in-cell touch panel and metal casing could affect both the handset's 4.7-inch and 5.5-inch models, with the problems considered to be more easily remedied in the smaller version.
For the larger version, there's also the matter of its sapphire-coated display not proving strong enough to pass drop tests. This, along with the other pressing issues, could lead to the larger device's not being released by the end of the year. But if it does get launched this year, Kuo predicts it will hit the market in the middle of the last quarter in limited quantities.
According to Kuo (via 9to5Mac):

We think the 5.5-inch model will also have issues with the yield rate of in-cell touch panel and color unevenness of metal casing. Indeed, these problems will likely be even more complicated with a larger size. In addition, from a technical perspective, we don’t expect sapphire cover, used for the first time on the 5.5-inch model, will easily pass the drop test near term. We are conservative about 5.5-inch iPhone launching by end-2014. Even if the product is launched in 2014, it is likely to take place after mid-4Q14, which is later than the September-October of consensus, with shipments being lower than consensus of 15- 20mn units.

The iPhone 6 is rumored to enter mass production this month and be unveiled by Apple at a special event in September. Both models of the smartphone are expected to feature thinner forms and the company's new A8 processors.
Last week, Kuo released a note saying that Apple's long-rumored "iWatch," which is also rumored to have a sapphire-coated display, will go into mass production in November, even as it's expected to be announced a month earlier.